Electrochemical immunosensor based on PtNPs/MoS@rGO composite for the detection of alpha-fetoprotein in human serum.

An electrochemical biosensor was created to identify the liver cancer marker alpha-fetoprotein (AFP) by employing nanocomposite materials. A combination of reduced graphene oxide (rGO) and molybdenum disulfide (MoS) was selected as the substrate material for the sensor to prepare the PtNPs/MoS@rGO electrochemical immunosensor. Among them, rGO has strong conductivity and MoS provides a large surface area for the anchoring of PtNPs for better attachment to the hybridized nanomaterials. Meanwhile, PtNPs exhibit consistent biocompatibility and excellent electrocatalytic activity. PtNPs also attach to hybrid nanomaterials and bind the antibody via the Pt-S bond, thereby furnishing the antibody with multiple binding sites for enhanced antibody adhesion. The immunosensor achieved ultra-sensitive AFP detection by exploiting the specific antigen-antibody binding. The structure and morphology of the PtNPs/MoS@rGO composites were investigated by transmission electron microscopy (TEM), energy dispersive X-ray (EDS) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy, and the sensor was electrochemically characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under optimized conditions, using differential pulse voltammetry the biosensor detected AFP in serum within a linear range of 1 ~ 10 pg/mL, with a correlation coefficient (r) of 0.9989, and a detection limit of 0.12 pg/mL (S/N = 3). The method offers a new approach for the ultrasensitive detection of serum AFP and is extremely selective, accurate, and precise with a relative standard deviation (RSD) of less than 6%. It has been successfully applied to the analysis of real human blood samples.